Organic metal perovskite materials are potential materials for solar cells due to their excellent physical properties. Organic lead halide perovskite has a higher efficiency over other perovskite materials. The major conventional method for forming a perovskite layer is coating. For example, two precursors of the perovskite are dissolved in an organic solvent (e.g. DMF), and then spin-coated on an electrode. Alternatively, lead halide (PbX2) can be dissolved in an organic solvent and spin-coated to form a PbX2 film on an electrode, and the PbX2 film is then dipped in methylammonium iodide (MAI) to form a perovskite film of Pb(CH3NH3)X2I. However, the solvent in the next coating step may dissolve the previously formed perovskite film formed previously. Even if the compositions in each of the coating processes are different, the solvent in different coating processes may dissolve the different compositions in previous coating processes. In short, the general coating processes cannot form a composition-gradient perovskite layer.
Accordingly, a novel method for manufacturing a composition-gradient perovskite layer is called-for.